The present invention relates to a flash memory device. Cell currents of an over-erased flash memory cell and cell currents of a plurality of weakly-programmed flash memory cells are compared by a plurality of comparators, and an low-voltage detector and a plurality of charge pump circuits are driven depending on the comparison result. Accordingly, a circuit that is not affected by variation in temperature, power supply voltage and process can be implemented. The threshold voltages of the flash memory cells are controlled to adjust a low-voltage detection point or a regulation point.